Although attempts have been made in the past to improve the quality of fat-free (non-fat) and low-fat cheese products, there are still a number of problems associated with these types of cheeses. These include pale or translucent color, tough or chewy texture, and poor melt and scorching/browning during baking (Tunick et al., 1991, Neth. Milk Dairy J. 45: 117-125). In addition, non-fat cheeses are often sticky; they stick to the manufacturing equipment, stick to other cheese such as on slices, or are sticky during consumption. These attributes are undesirable. Despite some improvements in the manufacture of processed cheese, for example as disclosed in U.S. Pat. Nos. 4,329,374; 4,459,313; 5,079,024; 5,225,220; and 5,374,443, the development of a high quality processed low-fat/non-fat cheese is desirable.
Monoglycerides (MG) and diglycerides (DG) are the most commonly used emulsifiers in the food industry and make up approximately 70% of the total world production of food emulsifiers. Monoglycerides and diglycerides are prepared by the interesterification of triglycerides (TG) with glycerol (Moonen and Hans, 2004, Emulsifiers in Food Technology, Whitehurst, ed. Blackwell Publishing, pp 41-58). Under alkaline conditions, the TG reacts with the glycerol at high temperatures (200-250° C.) resulting in a mixture of MG, DG and TG as well as a small proportion of unreacted glycerol. Commercial glyceride blends often contain about 45-55% MG, 38-45% DG, 8-12% TG and 1-7% free glycerol. Mono- and diglycerides are very efficient surfactants as they contain both hydrophilic and hydrophobic regions meaning that they are soluble in both oil and water.
Monoglycerides and diglycerides hold a GRAS status and are therefore generally recognized as safe for inclusion in food products. There are wide applications for MG and DG in the food industry. They are added to bakery products to act as dough conditioners and strengtheners, crumb softeners, and also to increase shelf life. In the dairy industry MG and DG have commonly been included in cheese spreads and ice cream, to impart a smoother and more uniform consistency. For example, U.S. Pat. No. 5,891,495 discloses the use of an oil-water emulsion of a diglyceride mixture, which mixture can also contain some monoglycerides, as an emulsion suitable as cream alternative for ice cream applications. However, a known problem is the fact that the addition of emulsifiers to processed cheese can bring about de-emulsification in the system, resulting in the formation of large pools of free oil during cheese cooking. Trace amounts (<0.2%) of emulsifiers have sometimes been added to some types of cheese products. Emulsifying salts or melting salts, such as sodium phosphates or citrates, are commonly used in process cheese and these salts disrupt caseins to help facilitate caseins acting as emulsifiers. These emulsifying salts are not true emulsifiers themselves.
When more than one surfactant is present in a system, they will compete for the interface. The surfactant that has the greatest ability to lower surface tension is preferentially adsorbed at the interface and if that surfactant is present at a sufficient quantity, it can prevent the adsorption of other surfactants. Low molecular weight products such as MG and DG are preferentially absorbed onto the interface over higher molecular weight surfactants, which in the case of milk is protein. This effect can be seen during ice cream production where MG and DG compete with proteins at the fat/water and the air/water interfaces.
It would be advantageous to develop new types of low-fat and/or fat-free processed cheese, with desirable textural attributes, color, and superior baking ability. The present invention addresses these and related needs.